Apparatus for distributing and spraying liquid or plastic coating compositions



July 12, 1938. E. A. JOHNSON 2,123,604

APPARATUS FOR DISTRIBUTING AND SPRAYING LIQUID OR PLASTIC COATINGCOMPOSITIONS Filed April 10, 1935 JNVENTOR. Earl f7. J'olms z ATTORNEYS.

Patented July 12, 1938 PATENT OFFICE APPARATUS FOR SPRAYING LIQUIDCOMPOSITIONS DISTRIBUTING AND OR PLASTIC COATING Earl A. Johnson,Dcarborn, Mich.

Application April 10,

5 Claims.

The present invention relates to an apparatus for distributing andspraying liquid or plastic coating compositions of the type of syntheticenamels or the like, where it is desirable to spray the composition onthe surface to be coated while the composition is maintained at asubstantially constant temperature.

It has been found that for satisfactory application of coatingcompositions of the type of a synthetic enamels or other resinousbodies, such compositions must be applied, while in a fluid condition,to the surface to be coated, and preferably at a temperature somewhatabove room temperature. It is desirable also to avoid variau tions inthe temperature of the composition as it leaves the nozzle of the spraygun, as otherwise undesirable variations will occur in the finish on thesurface. These undesirable variations in the finish can-be avoided bymaintaining the composition at a substantially constant heat as it issprayed from the nozzle of the spray gun.

In addition to maintaining this substantially constant heat, it isdesirable that an apparatus for handling such compositions shouldprevent the settling of the suspended solids such as pigments, fillersor the like which are incorporated in the coating composition. Suchsolids may settle out either in the supply tank or in the material hosesconnected with the supply tank or in the hose connecting the spray gunwith the supply line.

The apparatus of the present invention assures the maintenance of asubstantially uniform suspension of the suspended solids in the coatingcomposition until discharged through to the spraygun.

It is, therefore, an object of the present invention to provide anapparatus for handling and distributing liquid or plastic coatingcompositions in which a substantially constant heat is maintained onsuch composition until it is discharged from the spray gun.

It is a further object of the present invention to provide an apparatusfor handling and distributing liquid or plastic coating compositions inwhich the suspended solids in such compositions are maintained insuspension during the handling and distributing thereof.

A further object of the present invention is to provide an apparatus forhandling and distributing liquid or plastic coating compositions whichis such as to produce surface finishes superior to the finishes producedby the methods and apparatus heretofore employed for similar purposes.

Other objects of this invention will appear in 55 the followingdescription and appended claims,

1935, Serial No. 15,537

reference being had to the accompanying drawing forming a part of thisspecification.

The single figure is an elevation, partially in section, showing anapparatus embodying the invention and showing, by broken views, theattachment between the spraying gun and the supply tank and a sectionthrough a spray gun connected therewith.

Before explaining in detail the present invention it is to be understoodthat the invention is not limited in its application to the details ofconstruction and arrangement of parts illustrated in the accompanyingdrawing, since the invention is capable of other embodiments and ofbeing practiced or carried out in various ways. Also it is to beunderstood that the phraseology or terminology employed herein is forthe purpose of description and not of limitation, and it is not intendedto limit the invention claimed herein beyond the requirements of theprior art.

Referring more in detail to the drawing, I provide a container l0 whichacts as the supply reservoir for the liquid or plastic coatingcomposition which is to be employed in finishing the surface to becoated. The container i0 is placed inside a thermally insulatedreceptacle ll having spaced inner and outer walls and heat insulatingmaterial [2 disposed therebetween. Heating means such as electricallyactuated heating elements l3 are placed inside the receptacle II and arepositioned adjacent the container ill. The container I0 is supported inspaced relation to the bottom of the receptacle H by means of supportsI! secured therein. This permits the flow of heated air around all partsof the container in the receptacle.

A removable cover I5 is placed 'on the top of the container l0 and thereis secured to the cover for removal therewith a vent plug [6, a feedline I! and a return line Ill. The feed line H extends through the coverIE to a point adjacent the bottom of the container I 0 and is providedwith a screened inlet l9 which screens the materials as they go into thefeed line. The feed line ll connects with a constant pressure pump 2|,or other suitable means, for raising the material from the lower levelof the container l0 and deliver it to the spray gun.

In the embodiment of my invention here shown, I prefer to use a constantpressure feed pump 2i driven by an electric motor 22. Material passingfrom the pump 2| passes through a pressure gauge 23 and a globe valve 24which controls the flow of the material to the material supply line 25.

plying the composition to a surface, such for example as a pressurespray gun 28. A return line 21 leads from the spray gun 26 to thematerial return pipe l8 which extends through the cover l and dischargesthe material returning therefrom into the body of material containedwithin the container ID. The return fiow of material is controlled by aglobe valve 28 which connects the return line 21 with the materialreturn pipe IS. The valve 28 is provided with an opening (not shown) inthe gate so that a constant return of material is possible even thoughthe valve is in closed position. This opening acts as a by-pass andprevents building up damaging pressures in the lines and the spray gunin the event the equipment is operated when the valve 28 is closed.

The materials in the spray gun 26 are subjected upon discharge to a flowof heated air under pressure which is conveyed through an airline 30 toan air heating chamber 3| in which a staggered electrically actuatedheating element 32 is provided. Air passing through the chamber contactsthe heating element 32 and is heated to a predetermined. degree beforepassing from the chamber to the air supply line 33 which connects withthe spray gun 26. The heating of the air inthis mamier increases itsvelocity as well as insures that no chilling of the materials will occurwhen the materials are discharged from the spray gun 26. The temperatureof the heating elements 32 may be controlled by a suitable switch 34which is electrically connected therewith.

Any desired type of spray gun 26 may be employed in connection with anapparatus embodying the present invention. It is necessary, however,that it be adapted for use in connection with this apparatus byproviding therein a chamber 40 which communicates with the materialsupply line 25 to receive material therefrom and communicates with thematerial return line 2"? to discharge material thereto. In one suchspray gun the heated air from the air line 33 is dis charged through aplurality of ports M, which surround the chamber 30 and discharge at apoint adjacent the point where material is discharged from the chamber40. The use of the chamber 41? and the material return line 27 thusinsures a constant flow of heated materials from the tank ii) to the gun26 and prevents settling of materials either in the gun or in the linesleading thereto.

The materials in the container to may be maintained at relativelyconstant temperatures within predetermined limits by any suitable typeof temperature control apparatus, one type of which is here shown by wayof example and comprises a thermocouple having thermally responsiveelements 50 depending in the receptacle ill at a point adjacent thebottom thereof and adjacent the point of withdrawal of the liquid fromthe tank. The element 50 is electrically connected with a. controlswitch 5i which in turn is electrically connected with the heatingelements l3 and a source of electrical energy (not shown). The controlswitch 5i may be set to maintain predetermined but substantiallyconstant temperatures within the tank in.

An apparatus for conveying liquid or plastic coating compositions whichembodies the present invention as above described may be used with themethod of conveying and distributing such tion'which is maintained aslafluid at a substantially constant temperature, preferably above roomtemperatures. This heated material is constantly withdrawn from acentral supply reservoir and is conveyed through pipe lines to the pointof discharge to the surface to be covered. The required amount of suchheated material is drawn through the discharge means and sprayed on thesurface to be covered. The excess heated material which is notdischarged through the discharge means is returned through the dischargemeans to the central supply reservoir. Thus there is a constantcirculation of the materials both in the reservoir and in the feed line,the discharge means and the return line. In order to avoid chilling thecomposition at the point of discharge from the discharge means, the airwhich is utilized to carry the composition. from the discharge means isheated and maintained at a substantially constant temperature bysuitably controlled air heating means.

The operation of the .apparatus embodying the present invention issubstantially as follows: The heat control means Si is adjusted to provide a suitable substantially constant temperature in the electricheating coils i3 which heats the materials in the tank iii to atemperature preferably slightly in excess of 90 F. After the material inthetank I ii isheated to some suitable predetermined temperature, thepump 2i or other suitable conveying means is turned on and a supply ofthe material is withdrawn from the container to through the screenedinlet IQ of the feed line ii. In a suitable embodiment I have .provided,by way of example, a capacity of ten gallons in the tank i0 and acapacity of approximately two gallons per minute in the pump 20. Withthis arrangement, the materials in the tank are completely circulated atleast every five minutes, and oftener as the amount of material isdecreased. By varying the relative sizes of the container and theamounts of materials therein and the capacity of the pump, any desiredrate of circulation of the materials may be provided. Pressures in theline 25 are controlled by the ,valve 26 and the return valve 28. Thus, aconstant circulation of the material from. the tank is insuredthroughout thelength of the supply line 25. When the valve in thedischarge meanssuch as the gun 26, is closed, none of this material maybe discharged onto the surface to be coated, but the material passesfrom the chamber 4@ into the return line 21 and is returned to thecontainer Ill. By the provision of this return line it will be observedthat the body of liquid or plastic coating composition which is in thechamber 40 of the discharge means 26 at any time, is permitted to remainin that chamber but an instant before it is returned to the supply tank.Also, any excess of materials flowing to the chamber 40 is returned in asimilar manner, so that the temperature of Y determined temperature,which may be regulated and uniformly maintained. The constant return ofthe excess liquid or plastic coating composition fromthe chamber to thetank "I insures a constant agitation of the composition and thisfacilitates the maintenance of the pigment or filler particles in thesuspension without substantial settling thereof.

I claim:

1. An apparatus for spraying liquid or plastic coating compositions,including in combination a supply reservoir adapted to hold a quantityof such liquid or composition, an air bath around said reservoir,heating means in said bath enabling the same to heat the liquid orcomposition contained in said reservoir to a predetermined temperatureand to maintain said temperature substantially constant throughout theentire time of operation, an enclosed hydraulic circuit connected withsaid reservoir, a spray gun included in said hydraulic circuit, aconstant pressure pump for circulating constantly and repeatedly saidheated liquid or composition in said circuit and for producing apredetermined pressure therein, the rate of said circulation being inexcess of the maximum discharge rate of said spray gun and beingsufllcient to insure a substantially uniform temperature of said heatedliquid or composition throughout the entire circuit.

2. An apparatus for spraying liquid or plastic coating compositions,including in combination a closed supply reservoir adapted to hold aquantity of such liquid or composition, a fluid bath around saidreservoir, saidbath being thermally insulated from the outside, electricheating means in said bath to heat the liquid or composition containedin said reservoir to a predetermined temperature and to maintain saidtemperature substantially constant throughout the time of operation, anenclosed hydraulic circuit connected with said reservoir, a spray gunincluded in said hydraulic circuit, a constant pressure pump forcirculating constantly and repeatedly said heated liquid or compositionin said circuit and for producing a predetermined pressure therein, therate of said circulation being in excess of the maximum discharge rateof said spray gun and being suflicient to insure a substantially uniformtemperature of said heated liquid or composition throughout the entirecircuit.

3. An apparatus for spraying liquid or plastic coating compositions,including in combination a closed supply reservoir adapted to hold aquantity of such liquid or composition, an enclosed air bath around saidreservoir, said bath being thermally insulated from the outside, heatingmeans in said bath adapted to heat the air thereof and thus the contentsof said reservoir, a thermocouple in said reservoir, an electricalcontrol device electrically connected with said thermocouple and adaptedto control said heating means, in response to the operation of saidthermocouple, to maintain the contents of the reservvoir at asubstantially uniform temperature throughout the period of operation, anenclosed hydraulic circuit connected with said reservoir, a spray gunincluded in said circuit, a constant pressure pump for circulatingconstantly and repeatedly said heated liquid or composition in saidcircuit and for producing a predetermined pressure therein, the rate ofsaid circulation being in excess of the maximum discharge rate of saidspray gun and being suflicient to insure a substantially uniformtemperature of said heated liquid or composition throughout the entirecircuit.

4. An apparatus for spraying liquid or plastic coating compositions,including in combination a closed supply reservoir adapted to hold aquantity of such liquid or composition, an enclosed air bath around saidreservoir, said bath being thermally insulated from the outside, heatingmeans in said bath adapted to heat the air thereof and thus the contentsof said reservoir, a thermocouple in said reservoir, an adjustableelectrical control device electrically connected with said thermocoupleand adapted to control said heating means, in response to the operationof said thermocouple, to maintain the contents of the reservoir at asubstantially uniform predetermined temperature throughout the cycle ofoperation, an enclosed hydraulic circuit connected with said reservoir,a spray gun included in said circuit, a constant pressure pump forcirculating constantly and repeatedly said heated liquid or compositionin said circuit and for producing a predetermined pressure therein, therate of said circulation being suflicient to maintain the temperature ofthe heated liquid or composition at said gun substantially equal to thatat the reservoir in spite of the heat losses in said circuit, and meansdelivering heated air to said spray gun.

5. An apparatus for sprayingliquid or plastic coating compositions,including in combination a closed supply reservoir adapted to hold aquantity of such liquid or composition, a fluid bath around saidreservoir, said bath being thermally insulated from the outside,electric heating means in said bath to heat the liquid or compositioncontained in said reservoir to a predetermined temperature and tomaintain said temperature substantially constant throughout the time ofoperation, an enclosed hydraulic circuit connected with said reservoir,a spray gun included in said hydraulic circuit, a constant pressure pumpfor circulating constantly and repeatedly said heated liquid orcomposition in said circuit and for producing a predetermined pressuretherein, the rate of said circulation being in excess of the maximumdischarge rate of said spray gun and being suflicient to insurea'substantially uniform temperature of said heated liquid or compositionthroughout the entire circuit, and means for supplying heated air underpressure to said spray gun.

EARL A. JOHNSON.

